Biggest thing with long range shooting, it is a rabbit hole. Watch as many videos and read as much as you can. When you think you are ready to buy, hold off just a bit longer because chances are your mind will change. If not you will buy twice. In this sport it is much easier to buy once, cry once. Develop a preference of things you like and buying will be much simpler.. As you go and learn your tastes will expand.
Example is my action. I have a Big Horn Origin, which I love and is a great quality action. When I change barrel, I need to take my entire gun a apart when me personally I am over. Some don't care.
My Steps:
1.)Remove barreled action from chassis
2.)Take Scope off
3.)Remove Scope Rail
4.) Place action in vise ( while being carful not to snap trigger off, which happens)
5.) Remove and replace barrel ( Some times keeping the recoil lug from moving can be a pain.)
6.) Mess around with head spacing
7.) Reassemble it all and torque it all down.
Now if you spent a bit more you could save a lot of hassle and aggravation by something like a Terminus action where everything is integrated and barrel changes are a few set screws with a pre head spaced barrel. But it does come down to price ( everybody suffers from this) and what you are willing to deal with. All the production guns mentioned are excellent, but people are happier longer if they go with a custom build. Black Friday is coming!
Where to start for custom gun: This is middle ground so you can go up and down from here
Remington 700 Footprint Action in 6.5CM,
Razor Gen 2 4.5x 27 in MIls ( Pick a scope with a reticle you like, all top tier scopes will perform. Also check how you get zero)
M10 Scope Rings
Chassis- What ever you like, all preference
Trigger- Trigger Tech special or Diamond
Barrel- MTU or any heavy contour